netdev - Re: [PATCH V2 1/6] vhost: introduce vhost_call

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Message-ID: <871ee1c1-8cf7-3d9d-1892-5991b92e5db3@redhat.com>
Date:   Fri, 17 Jul 2020 11:32:08 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Zhu Lingshan <lingshan.zhu@...el.com>, mst@...hat.com,
        alex.williamson@...hat.com, pbonzini@...hat.com,
        sean.j.christopherson@...el.com, wanpengli@...cent.com
Cc:     virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH V2 1/6] vhost: introduce vhost_call_ctx


On 2020/7/16 下午7:23, Zhu Lingshan wrote:
> This commit introduces struct vhost_call_ctx which replaced
> raw struct eventfd_ctx *call_ctx in struct vhost_virtqueue.
> Besides eventfd_ctx, it contains a spin lock and an
> irq_bypass_producer in its structure.
>
> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
> Suggested-by: Jason Wang <jasowang@...hat.com>
> ---
>   drivers/vhost/vdpa.c  |  4 ++--
>   drivers/vhost/vhost.c | 22 ++++++++++++++++------
>   drivers/vhost/vhost.h |  9 ++++++++-
>   3 files changed, 26 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 7580e34..2fcc422 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -96,7 +96,7 @@ static void handle_vq_kick(struct vhost_work *work)
>   static irqreturn_t vhost_vdpa_virtqueue_cb(void *private)
>   {
>   	struct vhost_virtqueue *vq = private;
> -	struct eventfd_ctx *call_ctx = vq->call_ctx;
> +	struct eventfd_ctx *call_ctx = vq->call_ctx.ctx;
>   
>   	if (call_ctx)
>   		eventfd_signal(call_ctx, 1);
> @@ -382,7 +382,7 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
>   		break;
>   
>   	case VHOST_SET_VRING_CALL:
> -		if (vq->call_ctx) {
> +		if (vq->call_ctx.ctx) {
>   			cb.callback = vhost_vdpa_virtqueue_cb;
>   			cb.private = vq;
>   		} else {
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index d7b8df3..4004e94 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -298,6 +298,13 @@ static void vhost_vq_meta_reset(struct vhost_dev *d)
>   		__vhost_vq_meta_reset(d->vqs[i]);
>   }
>   
> +static void vhost_call_ctx_reset(struct vhost_call_ctx *call_ctx)
> +{
> +	call_ctx->ctx = NULL;
> +	memset(&call_ctx->producer, 0x0, sizeof(struct irq_bypass_producer));
> +	spin_lock_init(&call_ctx->ctx_lock);
> +}
> +
>   static void vhost_vq_reset(struct vhost_dev *dev,
>   			   struct vhost_virtqueue *vq)
>   {
> @@ -319,13 +326,13 @@ static void vhost_vq_reset(struct vhost_dev *dev,
>   	vq->log_base = NULL;
>   	vq->error_ctx = NULL;
>   	vq->kick = NULL;
> -	vq->call_ctx = NULL;
>   	vq->log_ctx = NULL;
>   	vhost_reset_is_le(vq);
>   	vhost_disable_cross_endian(vq);
>   	vq->busyloop_timeout = 0;
>   	vq->umem = NULL;
>   	vq->iotlb = NULL;
> +	vhost_call_ctx_reset(&vq->call_ctx);
>   	__vhost_vq_meta_reset(vq);
>   }
>   
> @@ -685,8 +692,8 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
>   			eventfd_ctx_put(dev->vqs[i]->error_ctx);
>   		if (dev->vqs[i]->kick)
>   			fput(dev->vqs[i]->kick);
> -		if (dev->vqs[i]->call_ctx)
> -			eventfd_ctx_put(dev->vqs[i]->call_ctx);
> +		if (dev->vqs[i]->call_ctx.ctx)
> +			eventfd_ctx_put(dev->vqs[i]->call_ctx.ctx);
>   		vhost_vq_reset(dev, dev->vqs[i]);
>   	}
>   	vhost_dev_free_iovecs(dev);
> @@ -1629,7 +1636,10 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
>   			r = PTR_ERR(ctx);
>   			break;
>   		}
> -		swap(ctx, vq->call_ctx);
> +
> +		spin_lock(&vq->call_ctx.ctx_lock);
> +		swap(ctx, vq->call_ctx.ctx);
> +		spin_unlock(&vq->call_ctx.ctx_lock);
>   		break;
>   	case VHOST_SET_VRING_ERR:
>   		if (copy_from_user(&f, argp, sizeof f)) {
> @@ -2440,8 +2450,8 @@ static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
>   void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
>   {
>   	/* Signal the Guest tell them we used something up. */
> -	if (vq->call_ctx && vhost_notify(dev, vq))
> -		eventfd_signal(vq->call_ctx, 1);
> +	if (vq->call_ctx.ctx && vhost_notify(dev, vq))
> +		eventfd_signal(vq->call_ctx.ctx, 1);
>   }
>   EXPORT_SYMBOL_GPL(vhost_signal);
>   
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index c8e96a0..402c62e 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -13,6 +13,7 @@
>   #include <linux/virtio_ring.h>
>   #include <linux/atomic.h>
>   #include <linux/vhost_iotlb.h>
> +#include <linux/irqbypass.h>
>   
>   struct vhost_work;
>   typedef void (*vhost_work_fn_t)(struct vhost_work *work);
> @@ -60,6 +61,12 @@ enum vhost_uaddr_type {
>   	VHOST_NUM_ADDRS = 3,
>   };
>   
> +struct vhost_call_ctx {


I think maybe "vhost_vring_call" is a better name since it contains not 
only the eventfd_ctx now.

Thanks


> +	struct eventfd_ctx *ctx;
> +	struct irq_bypass_producer producer;
> +	spinlock_t ctx_lock;
> +};
> +
>   /* The virtqueue structure describes a queue attached to a device. */
>   struct vhost_virtqueue {
>   	struct vhost_dev *dev;
> @@ -72,7 +79,7 @@ struct vhost_virtqueue {
>   	vring_used_t __user *used;
>   	const struct vhost_iotlb_map *meta_iotlb[VHOST_NUM_ADDRS];
>   	struct file *kick;
> -	struct eventfd_ctx *call_ctx;
> +	struct vhost_call_ctx call_ctx;
>   	struct eventfd_ctx *error_ctx;
>   	struct eventfd_ctx *log_ctx;
>